Reactor systems comprising multiple parallel reactors which are operated in parallel or sequentially are widely known. In such systems, the equal distribution of fluid to the reactors is important. In the past, solutions have been proposed involving the arrangement of flow restrictors such as capillaries in the reactor feed lines that bring the fluid from a common fluid source to the reactors. The fluid will be evenly distributed over the reactors if the capillaries all have substantially the same resistance to fluid flow and have the highest resistance to fluid flow in the system. This is for example described in WO99/64160.
In recent years, it has been proposed to use microfluidic chips as flow restrictors instead of capillaries. Microfluidic chips are easier to handle than capillaries and require less space when long flow restrictor channels are required. Microfluidic chips are also used in flow splitters, in which typically microfluidic chips are applied that have a single common inlet port and multiple outlet ports, with flow restrictor channels extending between the common inlet port and one of the outlet ports.
The microfluidic chips that are used in reactor systems of the type to which the invention pertains are different from the microfluidic chips that are used for “lab-on-chip”-purposes in that in microfluidic chips for “lab-on-chip”-purposes usually one or more of the channel in the chip are adapted to function as a reactor. In the microfluidic chips that are in reactor systems of the type to which the invention pertains the channels in the microfluidic chip merely function as conduits for the fluid flow and not as reactors; the system comprises one or more separate reactors in which the reaction takes place.
Microfluidic chips have some problems when they are applied in elevated pressure reactor systems, for example systems in which the pressure inside the microfluidic chip exceeds 30 bar. Many high throughput applications require operation pressures above 30 bar, sometimes even above 100 bar, up to for example 300 bar.
Microfluidic chips usually have a planar shape and are generally made from two or more layers of glass, silicon or quartz that are bonded together after a flow channel is etched in one or more of the layers. These materials allow to accurately make channels in them. When a high pressure fluid flow is present in the channel, the layers in the microfluidic chip may become delaminated. Also, there is a risk of cracks forming in the silicon, glass or quartz. These kinds of failures may result in leakage of the microfluidic chip, and even breaking of the microfluidic chip is possible. Unlike for example a metal microfluidic chip, glass, silicon or quartz microfluidic chips are brittle and may break without warning due to microscopic cracks that are not visible by the naked eye. Such cracks may have formed during previous load pressure cycles on the microfluidic chip. For example, when a microfluidic chip first is tested at for example 150 bar, the microfluidic chip may look fine after that test, but it may break when later just 100 bar is applied due to the microscopic cracks that were formed during the test at 150 bar.
Another problem associated with the use of microfluidic chips at elevated pressures is that the connections between the microfluidic chip and the flow lines that feed the channel in the microfluidic chip or receive fluid from the channel in the microfluidic chip are hard to make fluid tight. In order to prevent leakage of these connections, these connections are often glued, but this makes it harder to exchange the microfluidic chip in the system for another microfluidic chip. It can be desired to exchange the microfluidic chip in the system for another microfluidic chip for example if a different resistance to fluid flow is desired, if a channel in the microfluidic chip has become clogged up or if the microfluidic chip leaks or has otherwise failed.
US2010/0144539 discloses a system with parallel reactors that comprises a microfluidic chips that is used as a flow splitter. In order to be able to operate this system at elevated pressures, a housing is provided in this known system. The pressure sensitive components of the system, such as the reactor vessels, valves, couplings, fittings and the flow splitter are arranged in this housing. The housing is pressurized to a high pressure by means of an auxiliary gas, for example nitrogen gas (N2), which makes that the pressure sensitive components are subjected to just a small pressure differential.
This known system is rather complex, it poses a safety risk due to the rather large volume inside the housing that is brought to a high pressure and it is hard to detect the location of any leaks in the components and connections that are arranged inside the housing. Furthermore, an experiment cannot start before the housing is fully pressurized, which will take a while. This increases the time that is involved in conducting experiments.